Throughout history, many mercenary groups and armies have played a decisive role in major wars, sometimes far surpassing their regular counterparts on the battlefield. While none of them survive today – as the development of modern warfare and weapons made them obsolete – they’re still remembered as some of the most successful fighting units ever deployed.

10. Genoese Crossbowmen

The Genoese crossbowmen were one of the most skilled and accomplished elite forces in medieval Europe. They were known for their expertise in naval warfare, and were considered better than any other archer unit on the continent. Their superiority came from the inherent advantage of their weapon – the crossbow could fire more than six shots per minute! 

Formed in 1338, Genoese crossbowmen protected the Republic of Genoa and acted as mercenaries for various Italian city states and European monarchies. They were highly sought-after for their superior archery skills, and a typical unit was composed of the shooter and two assistants; one supporting the shield and the other handling a second bow to increase the rate of fire. 

9. Winged Hussars

The Winged Hussars were an elite branch of the Polish military, originating in the 16th century as exiled Balkan mercenaries. Equipped with long lances and elaborate armor, the hussars adopted winged uniforms that served both as a terrifying tactic and protection, giving them their famous name. 

It was a heavy shock cavalry renowned for its powerful charges, often impaling multiple enemies with a single lance. The Hussars won many battles over the years, including the famous Battle of Vienna in 1683, where they played a decisive role in the defeat of the Ottoman forces.

Despite their initial successes, however, the Hussars started losing their edge with the advent of firearms and new military formations. They couldn’t adapt to the changing battlefield, leading to their eventual decline. Their appearance and reputation as a successful Polish unit persisted, however, as they’re still an integral part of the combined history of the Polish-Lithuanian empire. 

8. Landsknechte

Landsknechte were highly-skilled mercenaries originating in southern Germany, serving as heavily-armed pikemen and elite foot soldiers across Europe during the late 15th to early-16th centuries. While they were originally formed to fight in the armies of the Holy Roman Emperor, Maximilian I, their exceptional skill on the battlefield made them sought-after mercenaries across Europe. Additionally, their fabulous attire, which included oversized flat hats, colorful clothing, and billowing sleeves, sealed their reputation as one of the most well-dressed fighting units of all time. 

The Landsknechte fought in a special pike-square formation, wielding weapons like the steel-tipped pike, the zweihänder (a broadsword), the katzbalger (a short sword), and the arquebus (an early matchlock musket). Their effectiveness with the formation and ability to adapt to Swiss pike tactics resulted in many military successes. Like other pre-gunpowder units of that time, however, changes in tactics and the emergence of firearms led to their eventual downfall. 

7. Ten Thousand

The Ten Thousand were a Greek mercenary division that played a major role during the rebellion of Prince Cyrus of Persia in 401 BC. Made up of 10,000 Greek soldiers and accompanied by close to 100,000 native troops, Cyrus marched towards Babylon in a bid to overthrow his brother, and gain control of the Persian Empire. While he was defeated and killed in one of the battles, the Greek mercenaries managed to win on their own flank, distinguishing themselves as a successful unit of the campaign. 

Before the fifth century BC, mercenaries were relatively scarce throughout the ancient-Greek region and were mainly employed by tyrants and kings, as city-states relied on citizen militias for their defense. It changed after the protracted conflict between Athens and Sparta, which militarized the region and led to many young men joining the armed forces, leading to a surge in the number of mercenaries across the Hellenic world, especially from the more impoverished areas like Thrace. 

6. Condottieri

The condottieri were leaders of mercenary bands in Italy from the mid-14th to 16th centuries. Initially made of foreign fighters, these mercenary armies were hired by Italian states through contracts called condottas. Englishman Sir John Hawkwood and Italians like Muzio Attendolo Sforza and Braccio da Montone were some of the more renowned and militarily-successful condottieri. Sadly, at least for their clients, they were also known for their disorderly behavior and propensity for changing sides for quick personal gains. 

The practice of hiring mercenaries by feudal lords and cities across Europe started in the 11th century, largely due to the increasing number of feuds. The condottieri, as leaders of these mercenary forces, usually had significant leverage over their clients, and were known to betray or even seize power from them. They also feature in Machiavelli’s works, who extensively talked about their actions and the tactical disadvantages that came with hiring them.

5. Gurkhas

The Gurkhas are fighting units that originated in the Nepalese town of Gorkha. While they fought and lost against the British in the Gurkha War of 1814-16, the British officers were impressed by their fighting skills. As a part of the peace treaty, many of these fighters joined the Company’s forces as mercenaries. 

Over the years, the Gurkhas have proven their abilities in many successful British military operations, including both of the world wars. They could be recognized by their signature  eighteen-inch knife called kukri. More than 19,000 have been killed in British service, though they have been hired by forces of other countries, too, like Singapore, Malaysia, and India. While the Gurkhas originally started out as mercenaries, there’s an ongoing debate around whether they should be designated as a regular part of the British Army due to their contributions.

4. Flying Tigers

The Flying Tigers were a renowned American volunteer group that operated during World War II. Formed in 1941, the group comprised volunteer pilots dispatched to the Chinese front to assist in the defense against Japan. Led by Lieutenant General Claire Lee Chennault, the Flying Tigers played an important role in the early stages of the war in the Pacific.

The Flying Tigers were known for their distinctive shark-faced fighter planes equipped with American-made Curtiss P-40 Warhawks. The group carried out multiple aerial combat missions against Japanese forces throughout the war, despite being outnumbered and facing superior enemy aircraft most of the time. 

3. Varangian Guard

The Varangian Guard was an elite army corps and personal bodyguards to the Byzantine emperor, starting with Basil II in 988 AD. Originally made of Viking warriors known for their expertise with double-bladed battle-axes, the group eventually gained a reputation for their effectiveness in battle. One of their most notable recruits was Harald Hardrada, who’d later become the king of Norway from 1046 to 1066 AD.

The Guard – permanently stationed at the Great Palace of Constantinople – primarily served as shock troops and protectors to the Byzantine throne. They played a major role in the protection of the empire, and were famous for their distinctive weapons and armor, which included shields and the rhomphaia – a one-edged sword. Members of the guard were granted unique privileges, like the ability to seize gold from the imperial treasury upon the death of the emperor. 

2. Grand Catalan Company

Catalan company, also called the Catalan Company of the East or the Grand Catalan Company, was one of the more-famous mercenary military groups in Europe around the 14th century. Composed mainly of soldiers from Catalonia and Aragon, the company operated as a private military in various conflicts in the eastern Mediterranean region.

The Catalan Company was formed in 1302 by veterans of the War of the Sicilian Vespers, which had left many of them unemployed. They initially served as a defense force for the Kingdom of Sicily, though soon transitioned into a powerful mercenary army of their own, seeking employment and contracts across the Mediterranean. Thanks to their reputation for discipline and tactics on the battlefield, the company remained in high demand throughout much of the middle ages. 

While the Catalans won many military successes, their personal ambitions eventually led to tensions with their Byzantine employers. In 1311, they rebelled against the emperor, as they plundered the Duchy of Athens and established their own rule between 1311 and 1388.

1. Swiss Pikemen

After its independence from the Holy Roman Empire in the 14th century, the Swiss Confederacy established one of the most successful fighting forces in history. Swiss soldiers, known for their self-reliance and resilience in harsh conditions, initially used halberds and crossbows, and even swords, war clubs, and flails.

Swiss commanders were known for their understanding of the terrain, as they regularly won victories against vastly-superior forces by their innovative, terrain-specific tactics. The Battle of Arbedo in 1422 marked a turning point, as this was when they first adopted the pike as their primary weapon. The pike formations, fought in deep columns, proved highly effective in offense and defense, leading to many notable military victories. Their reputation extended far beyond their homeland, as Swiss mercenaries were sought-after by armies across Europe.

Colombia, Poland, Venezuela, Ireland, Sweden, Morocco—the list goes on. For hundreds of years, Scottish soldiers have taken the opportunity to earn money by fighting in foreign lands. In other words, they were mercenaries. Sometimes these Scottish soldiers of fortune supported established monarchs, while on other occasions, they fought with rebels anxious to upend the status quo. But wherever they went and whoever they fought, the results most often were tales well worth the telling.

10 Peter McAleese

A Glaswegian born in 1942, Peter Maltese led a band of mercenary fighters to Colombia in 1989. McAleese had an impressive pedigree for his role as the commander of a motley bunch of soldiers of fortune. He’d served with Britain’s feted elite force, the SAS. In a documentary film about his life, McAleese reinforced his image as an all-around tough guy, saying, “I was trained to kill by the Army, but the fighting instinct came from Glasgow.”

McAleese left the army in 1969 and drifted into the shadowy world of mercenary fighters, seeing action in African hotspots such as Angola and what was then Rhodesia and is now Zimbabwe. But why did he travel to Colombia? In a barely credible turn of events, he’d been hired by the Cali Cartel to kill the leader of its main rival, the Medellin Cartel. In other words, McAleese’s mission was no less than to assassinate Pablo Escobar. The Scotsman and his buddies were to helicopter into Escobar’s compound. But McAleese’s chopper crashed in the Andes, injuring him badly. The plot was aborted. McAleese escaped and died in 2021, aged 79. Escobar was killed in a gun battle in 1993.^[1]

9 Gregor MacGregor, Prince of Poyais

Born on Christmas Eve 1786, Gregor MacGregor launched his military career conventionally enough by joining the British Army’s 57th Foot Regiment while still only a 16-year-old. The young man saw action in the Napoleonic Wars and eventually attained the rank of major before hanging up his sword in 1810. For his next adventure, his eyes turned to South America, and he arrived in Venezuela in 1812.
MacGregor was acquainted with the revolutionary leader General Francisco de Miranda, who accepted him into his forces as a colonel in the fight against the Spanish colonialists. MacGregor, who had awarded himself a knighthood, rose to be a general in the Venezuelan Army. His exploits included an attempt to seize Florida from the Spanish and a bid to found a colony in Nicaragua.

His most grandiose scheme, however, saw him taking the title of Prince of Poyais as he developed a colony in the Bay of Honduras. To do so, he enticed gullible British investors and prospective colonizers with false claims. They lost all their money, and the colony was a total disaster. Somehow, “Prince” Gregor walked away unscathed.^[2]

8 Patrick Leopold Gordon of Auchleuchries

Born in the northeast of Scotland in 1635, Patrick Gordon first left his native land while still a teenager. He traveled to the Polish city of what was then Danzig and is now Gdańsk, where he enrolled at a Jesuit college. A war between Poland and Sweden erupted in 1655, and that was when the young Gordon first became a mercenary. It seems he was none too choosy about who his employers were since he fought on both sides during the hostilities.

In 1661, Gordon walked away from both Poland and Sweden, electing to join the Russian army. With the rank of major, he gave useful service in 1661 by crushing civil disturbances in Moscow. After Peter the Great came to power in 1696, Gordon became a key adviser and even friend to the young Tsar, earning the rank of general. He played an important part in suppressing an attempted palace coup against Peter in 1698. He died a year later.^[3]

7 James Francis Edward Keith

Keith was a high-born Scot, the second son of the 9th Earl Marischal of Scotland. Despite that, he was forced to leave his homeland after becoming involved in the unsuccessful Jacobite attempt to seize the British throne in 1715. Fleeing to France, Keith ended up in Spain, where he became an officer in the Spanish Army. But since he was a Protestant in a Catholic country, his prospects were poor, so he left for Russia.

In 1728, Keith was made a colonel of a Russian regiment and fought against the Swedes. After his time with the Russians, it seems that Keith was keen for new pastures, and he joined the Prussian Army, seeing extensive action in the Seven Years’ War that convulsed much of Europe and North America. By now a Field Marshall, Keith fought at the 1758 Battle of Hochkirch in Germany when 80,000 Austrians faced 31,000 Prussians. The Austrians routed the Prussians killing 9,000 of them, including Keith.^[4]

6 Archibald Ruthven of Forteviot

Archibald Ruthven was born into a distinguished Scottish family—his father was Lord Ruthven. In 1572, Ruthven sailed for Scandinavia, where he accepted a post in the army of the Swedish king, Johan III. Johan’s first order was that the Scot should return to his homeland to recruit 2,000 mercenaries. In the event, he returned to Sweden with nearly 4,000 soldiers.

Ruthven became embroiled in a bitter dispute about his soldiers’ pay which resulted in the execution of one Scottish officer for embezzlement, Hugh Cahun. Before he was put to death, Cahun accused Ruthven, baselessly as far as we know, of plotting the assassination of King Johan. Apparently in the clear, Ruthven now sailed for Livonia on the Baltic Sea with his troops. There, a bitter dispute with their German allies resulted in the deaths of some 1,500 men. The upshot of this deadly squabble was that Ruthven was again accused of plotting against Johan. Despite his denials, the unfortunate Scot was imprisoned and died in jail.^[5]

5 Sir Harry Aubrey de Vere Maclean

Born into a well-to-do Scots family in 1848, the splendidly named Sir Harry Aubrey de Vere Maclean joined the British Army in 1869 and saw service in Canada, Gibraltar, and Bermuda. After seven years in the army, Maclean resigned his commission and accepted the position of a drill instructor in the army of the Sultan of Morocco, Mawlay Hassan.

Not long after he arrived in Tangier, Mclean took command of 400 infantry troops, with an increase in pay dependent on him learning Arabic, which he did. Abdul-Aziz succeeded Hussain as the sultan and retained Mclean’s services, sending him on missions to various Moroccan provinces. But life in Morocco was not without its perils; in 1907, the Scotsman was kidnapped and held for ransom for seven months. The following year Abdul-Aziz was deposed by his own brother Mawlay Abdul-Hafiz. The new sultan was minded to keep Mclean on, but the two couldn’t agree on a contract, so Mclean resigned, living out his days in Tangier until his death in 1920.^[6]

4 Peter Duffy

Raised in the northern Scottish town of Elgin, Peter Duffy was born into some privilege in 1941. He was sent to Gordonstoun, the same private school that King Charles attended a few years after. Later in life, Duffy was second-in-command of a group of mercenaries who went to engineer a coup in Seychelles Island in 1981.

Duffy’s commander was “Mad” Mike Hoare, a notorious mercenary of many years. Hoare and Duffy led a group of fighters drawn from ex-Rhodesian soldiers and ex-South African special forces. Armed to the teeth, the men flew into Seychelles aboard a commercial flight. Unfortunately for Duffy and his comrades, an airport official noticed an AK-47 in one man’s luggage. A gunfight ensued, and Duffy and others made good their escape by hijacking an Air India plane, leaving behind one dead comrade. Several of the conspirators were tried the next year in South Africa. Duffy got five years, Hoare 10. Duffy died a broken man in 1981.^[7]

3 George Sinclair

In 1612, Captain George Sinclair sailed from Scotland with a troop of Scottish mercenaries that he’d recruited in Caithness in the Scottish Highlands. They were to join the cause of King Charles IX of Sweden, who was fighting his neighbor Christian IV of Denmark. Sinclair and some 300 men landed in Norway with the intention of marching to Sweden.

The Scots had not bargained for the possibility that the Norwegians might not take kindly to a mercenary force tramping across their country. As it happened, the Norwegians were not at all happy. Seven days after Sinclair and his men had arrived on Norwegian soil, a local force launched a deadly ambush. As the Scots entered a narrow valley, the Norwegians rolled boulders down the slopes to block their escape routes. Once the rocks had been unleashed, musketeers picked off the mercenaries, killing more than 150. Sinclair was shot dead by a man named Berdon Sejelstad. The Scotsman’s wife and child, who had unwisely accompanied the ill-fated expedition, were also killed, although not before the woman had stabbed one of the Norwegians to death.^[8]

2 Redshanks

The Redshanks were mercenaries mostly recruited from the islands of the Hebrides off the coast of northwest Scotland, although mainland Highlanders joined in as well. In the 16th century, they went to fight for the Irish as they opposed the English invaders of the Emerald Isle. Life in the Highlands and islands of Scotland could be very tough, and men were glad to earn money paid to those who fought for Irish lords.

In one case, a regiment of Highland fighters came as a kind of wedding present. That was in 1569 when the Scottish Lady Agnes Campbell, daughter of the Earl of Argyll, married the Irish nobleman and chief Turlough Luineach O’Neill. She brought 1,200 Scottish mercenaries to the marriage. Unsurprisingly, the English were none too happy about the continual influx of Highland warriors arriving in Ireland. From the late 16th century, the English authorities began to pay off Highland clan chieftains. The payments—bribes might be the correct word—were made on the condition that the chiefs kept their men at home.^[9]

1 Alexander Leslie of Auchintoul

Alexander Leslie of Auchintoul was born into a landowning Scots family in 1590—Auchintoul is in the northeast of Scotland. Leslie started out fighting for the Poles in 1618 when he was captured by the Russians. They released him, and by 1629, he was employed by the Swedes. The Swedish king, Gustav II Adolf, sent him to Moscow, and Leslie tarried there in the service of the Tsar.

The Smolensk War, a conflict between Poland and Russia, broke out in 1632, and Leslie brought regiments of mercenaries from European countries, including England and Scotland, to fight for the Tsar. Returning to Scotland in 1637, Leslie embroiled himself in the Civil War of the time, on the wrong side. Captured in battle in the Scottish Borders, he narrowly escaped execution, the fate of many of his comrades. However, he was banished and never allowed to return to Scotland. Leslie returned to Russia, where he achieved the rank of general, the first Scot to do so. His achievements included seizing Smolensk from Polish control in 1654.^[10]